<?php

class JSSDK
{

    private $appId;

    private $appSecret;

    public function __construct($appId, $appSecret)
    {
        $this->appId = $appId;
        $this->appSecret = $appSecret;
    }

    public function getSignPackage()
    {
        $jsapiTicket = $this->getJsApiTicket();
        
        // 注意 URL 一定要动态获取，不能 hardcode.
        $protocol = (! empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off' || $_SERVER['SERVER_PORT'] == 443) ? "https://" : "http://";
        $url = "{$protocol}{$_SERVER[HTTP_HOST]}{$_SERVER[REQUEST_URI]}";
        
        $timestamp = time();
        $nonceStr = $this->createNonceStr();
        
        // 这里参数的顺序要按照 key 值 ASCII 码升序排序
        $string = "jsapi_ticket={$jsapiTicket}&noncestr={$nonceStr}&timestamp={$timestamp}&url={$url}";
        
        $signature = sha1($string);
        
        $signPackage = array(
            "appId" => $this->appId,
            "nonceStr" => $nonceStr,
            "timestamp" => $timestamp,
            "url" => $url,
            "signature" => $signature,
            "rawString" => $string
        );
        
        return $signPackage;
    }

    private function createNonceStr($length = 16)
    {
        $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        
        $str = "";
        for ($i = 0; $i < $length; $i ++) {
            $str .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);
        }
        
        return $str;
    }

    public function getJsApiTicket()
    {
        // jsapi_ticket 应该全局存储与更新，以下代码以写入到文件中做示例
        $data = json_decode(file_get_contents(ROOTPATH . '/_cache/token/jsapi_ticket.json'));
        
        if ($data->expire_time < time()) {
            $accessToken = $this->getAccessToken();
            
            // 如果是企业号用以下 URL 获取 ticket
            // $url = "https://qyapi.weixin.qq.com/cgi-bin/get_jsapi_ticket?access_token=$accessToken";
            $url = "https://api.weixin.qq.com/cgi-bin/ticket/getticket?type=jsapi&access_token={$accessToken}";
            $res = json_decode($this->httpGet($url));
            $ticket = $res->ticket;
            
            if ($ticket) {
                $data->expire_time = time() + 5000;
                $data->jsapi_ticket = $ticket;
                
                if (! is_dir(ROOTPATH . '/_cache/token')) {
                    $res = @mkdir(ROOTPATH . '/_cache/token', 0777, true);
                    @chown(ROOTPATH . '/_cache/token', 'apache');
                }
                
                $fp = fopen(ROOTPATH . '/_cache/token/jsapi_ticket.json', 'w');
                fwrite($fp, json_encode($data));
                fclose($fp);
            }
        } else
            $ticket = $data->jsapi_ticket;
        
        return $ticket;
    }

    private function getAccessToken()
    {
        return wx_api_token($this->appId, $this->appSecret);
    }

    private function httpGet($url)
    {
        $curl = curl_init();
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($curl, CURLOPT_TIMEOUT, 500);
        curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, false);
        curl_setopt($curl, CURLOPT_URL, $url);
        
        $res = curl_exec($curl);
        curl_close($curl);
        
        return $res;
    }
}
?>